Thin film devices comprising device layers deposited on CMOS substrates are well-known. Such a thin film device is manufactured by stacking a plurality of device layers in order on a substrate. Such devices include memory elements, sensors, emitters, etc.
Consider the example of an MRAM thin film device including a resistive cross point array of spin dependent tunneling (SDT) junctions, word lines extending along rows of the SDT junctions, and bit lines extending along columns of the SDT junctions. Each SDT junction is located at a cross point of a word line and a bit line. The magnetization of each SDT junction assumes one of two stable orientations at any given time. These two stable orientations, parallel and anti-parallel, represent logic values of ‘0’ and ‘1’. The magnetization orientation, in turn, affects the resistance of the SDT junction. Resistance of the SDT junction is a first value (R) if the magnetization orientation is parallel and a second value (R+ΔR) if the magnetization orientation is anti-parallel. The magnetization orientation of the SDT junction and, therefore, its logic value may be read by sensing its resistance state.
A write operation on a selected SDT junction is performed by supplying write currents to the word and bit lines crossing the selected SDT junction. The currents create two external magnetic fields that, when combined, switch the magnetization orientation of the selected SDT junction from parallel to anti-parallel or vice versa.
Too small a write current might not cause the selected SDT junction to change its magnetization orientation. Conventional MRAM designs sometimes need one or two current driven magnetic fields to switch the magnetization orientation. However, the magnitude of the current(s) needed to switch the magnetization orientation is too high to maintain the cost advantage of the implementation of the MRAM device. Furthermore, as technology develops, this problem will be exacerbated.
Accordingly, what is needed is a thin film device and a method of implementation thereof that addresses the above described problem related to MRAM devices. The present invention addresses this need.